John T. Hardy

Sea-surface microlayer metals enrichments in an urban and rural bay☆

The sea-surface microlayer is an important interface between the atmosphere and ocean and a collection point for many anthropogenic materials including potentially toxic metals. We developed a glass plate sampler to collect the upper 30 to 55 micrometers of the sea surface. Samples of the microlayer and subsurface bulk water from an urban and rural bay were analysed for concentrations of Pb, Zn, Cu, Cd and Fe. Metal concentrations in both the microlayer and bulk water were generally 2 to 15 times greater in the urban than in the rural bay. Concentrations of metals in the microlayer of both bays averaged 6 to 65 times greater than those in the bulk water. In the urban bay, microlayer concentrations of Pb, Zn and Cu from 10 to > 100 μg 1−1 were common. Measured microlayer metals concentrations agree well with those predicted from atmospheric deposition rates using a previously derived empirical model developed from laboratory microcosm studies. Further work will be required to determine whether or not these high microlayer metal concentrations contain significant biologically available fractions which could impact fisheries recruitment of larval icthyoneuston.

Contaminant concentrations and toxicity of sea-surface microlayer near Los Angeles, California

Abstract Sea-surface microlayer samples were collected from six nearshore areas receiving different amounts of anthropogenic inputs. The samples were analyzed for selected trace metals, chlorinated hydrocarbons, and polycyclic aromatic hydrocarbons. The relative toxicities of the samples were determined with fish embryo bioassays. Contaminant concentrations generally increased from offshore to the inshore stations. Contaminant concentrations were several orders of magnitude higher in microlayer samples from the highly industrialized Los Angeles and Long Beach harbors compared to samples from a site 15km offshore. Microlayer samples from the inshore stations were significantly more toxic, and induced significantly more developmental abnormalities and chromosome aberrations, than samples from the offshore stations.

Clam burrowing behaviour: inhibition by copper-enriched sediment

Burrowing behaviour is adaptive and allows clams to escape predation; yet the effects of potentially toxic metals on such behaviour have not been adequately investigated. In natural marine sediment contaminated with copper the time for littleneck clams (Protothaca staminea) to achieve complete burial was recorded. Above a threshold of 5.8 μg g−1 Cu added to dry sediment, the time for 50% of the clams to burrow (ET50) increased logarithmically with increasing sediment copper concentration according to: logET50 = 0.15 (CU) - 1.37 (n = 4, r2 = 0.98) where ET50=time in hours for 50% of clams to burrow and Cu=μg g−1 Cu in dry sediment. Previously exposed clams had both a lower threshold to Cu and a longer reburrowing time (ET50). Clams exposed to sediment mixed with Chelex-100®-sorbed copper showed no significant change in burrowing time. Bioassays based on claim burrowing behaviour can measure both bioeffectiveness of sediment-sorbed metals and a sublethal effect with ecological meaning.

Aquatic surface microlayer contamination in chesapeake bay

Abstract The aquatic surface microlayer (SMIC), ∼50 μm thick, serves as a concentration point for metal and organic contaminants that have low water solubility or are associated with floatable particles. Also, the eggs and larvae of many fish and shellfish species float on, or come in contact with, the water surface throughout their early development. The objectives of this study were (1) to determine the present degree of aquatic surface microlayer pollution at selected sites in Chesapeake Bay, and (2) to provide a preliminary evaluation of sources contributing to any observed contamination. Twelve stations located in urban bays, major rivers, and the north central bay were sampled three times, each at ∼5-day intervals during May 1986. Samples of 1.4–4.1 each were collected from the upper 30–60-μm water surface (surface microlayer, SMIC) using a Teflon-coated rotating drum microlayer sampler. One sample of subsurface water was collected in the central bay. At all stations, concentrations of metals, alkanes, and aromatic hydrocarbons in the SMIC were high compared with one bulk-water sample and with typical concentrations in water of Chesapeake Bay and elsewhere. SMIC contamination varied greatly among the three sampling times, but high mean contaminant levels (total polycyclic aromatic hydrocarbons, 1.9–6.2 μg 1 −1 ; Pb, 4.9–24 μg 1 −1 ; Cu, 4–16 μg 1 −1 ; and Zn, 34–59 μg 1 −1 ) were found at the upper Potomac and northern bay sites. Three separate areas were identified on the basis of relative concentrations of different aromatic hydrocarbons in SMIC samples - the northern bay, the Potomac River, and the cleaner southern and eastern portions of the sampling area. Suspected sources of surface contamination include gasoline and diesel fuel combustion, coal combustion, and petroleum product releases. Concentrations of metals and hydrocarbons, at approximately half the stations sampled, are sufficient to pose a threat to the reproductive stages of some fish and shellfish. Sampling and analysis of the surface microlayer provides a sensitive tool for source identification and monitoring of potentially harmful aquatic pollution.

The sea-surface microlayer of puget sound: Part II. Concentrations of contaminants and relation to toxicity

Abstract Many aquatic contaminants, because of low water solubility (hydrophobicity) or association with floatable particles, concentrate at the sea surface. Thirty-six samples of the sea-surface microlayer (SMIC), the upper 50 μm, were collected from sites in Puget Sound, Washington State. Sites included three urban bays, central Puget Sound, and a rural reference site. Exposure of floating fish eggs to approximately half of these samples resulted in sublethal and lethal toxic effects (Hardy et al., 1987c). Chemical analyses revealed high concentrations of contaminants in many of the samples. Major temporal and spatial differences in sea-surface chemistry occurred, but maximum (for all) and mean (for 1985) concentrations were aromatic hydrocarbons, 8030 (mean 132) μg liter−1: saturate hydrocarbons, 2060 μg liter−1: pesticides, 43·8 (mean 0·46) ng liter−1; PCBs, 3890 (mean 631) ng liter−1; and total metals, 4750 (mean 626) μg liter−1. Stepwise multivariate regression indicated that the percentage of fish eggs developing to normal live larvae decreased with increasing concentrations of a complex mixture of contaminants. Principal component analysis demonstrated that the major types of contaminants did not differ greatly in their statistical contribution to the toxicity, i.e. no single chemical was responsible for the observed toxicity. The chemical composition of the SMIC samples suggested that contamination originated from a variety of sources including atmospheric deposition, terrestrial runoff of fossil fuel combustion products, and sewage disposal.

Is atmospheric particulate matter inhibiting marine primary productivity

Present deposition rates of atmospheric particulate matter do not appear great enough to inhibit marine primary productivity except, perhaps, at the sea-surface microlayer. Milligram/liter quantities of air particulate matter added to seawater result in an exponential reduction in photosynthetic /sup 14/C assimilation of natural marine phytoplankton populations. Urban particles are 6 times more toxic than rural particles. The ratios of soluble trace elements from equal amounts of urban (Seattle) to rural (Quillayute) atmospheric particles are as follows: As, 112; Br, 6.4; Cr, 3.4; Cu, 3.7; Ni, 3.0; Pb, 36; V, 2.7; and Zn, 2.2.

Copper bioavailability to marine bivalves and shrimp: Relationship to cupric ion activity

Abstract Studies were performed to determine the effects of dissolved substances present in natural seawater and sediment on the bioavailability of added Cu +2 . Whole clams Macoma inquinata and shrimp, Pandalus danae , were exposed to four concentrations of Cu in a flow-through seawater system. Bioaccumulation of Cu was reduced in shrimp, Pandalus danae , clams, M. inquinata , and excised clam gills, Protothaca staminea , exposed to an aged, compared with an unaged, Cu-seawater solution. This is thought to be due to slow complexation of the Cu by dissolved substances present in natural seawater. In a static system, with added sediment, more than 50% of the added Cu +2 became bound to the organic fraction of the sediment and was unavailable to suspension feeding clams, Protothaca staminea . In contrast, deposit feeding clams, Macoma inquinata , placed in the sediment approximately doubled in Cu body burden within two months. Complexed Cu appears to be less bioavailable than ionic Cu and hence measurements of ionic and weakly complexed Cu by differential pulse anodic stripping voltametry provide a better prediction of bioavailable Cu than conventional measurements of total Cu-seawater concentrations.

The sea-surface microlayer of puget sound: Part I. Toxic effects on fish eggs and larvae

Abstract The sea surface is an important habitat for the developmental stages (eggs and larvae) of many fish and invertebrates; it is also a concentration point for anthropogenic contaminants entering the sea. Studies were conducted to determine the extent to which the sea surface of Puget Sound was toxic to the early life history stages of fish. Three urban bays with suspected contamination, a rural reference bay, and a Central Sound site were compared. Surface-dwelling eggs and organisms (zooneuston) were collected with a surface-skimming neuston net and their densities enumerated. Sand sole ( Psettichthys melanostictus ) embryos were exposed in the field and laboratory to the sea-surface microlayer. To develop a useful year-round approach to monitoring sea-surface toxicity, larval development of anchovies, kelp bass, and sea urchins was also evaluated as an indication of sea-surface microlayer toxicity. During the spawning season (February and March), urban boys in Puget Sound had lower concentrations of sand sole eggs and neustonic organisms on the sea surface than did the rural bayor Central Sound reference sites. Compared to the reference sites, laboratory exposure to surface microlayer samples collected from urban bay sites generally resulted in more chromsomal aberrations in developing sole embryos, reduced hatching success of sole larvae, and reduced growth in trout cell cultures. In situ hatching success of sole eggs was reduced by half or more in urban bays compared to reference sites. Toxicity was associated with visible surface slicks and, in urban bays, increased with increasing surface pressure (dynes cm −1 ). Results to be reported separately (Part II) indicate that toxicity is strongly correlated with the presence of high concentrations of polycyclic aromatic hydrocarbons and metals in the sea-surface microlayer. The toxicity of SMIC samples was similar when evaluated by sole, anchovy, kelp bass, or sea urchin tests. A sea-surface monitoring program could use sea urchin embryos to evaluate site-specific sea-surface toxicity throughout the year.

Clam burrowing behaviour and mortality related to sediment copper

Abstract Gravel sediment freshly enriched with over 4.4 μg Cu g−1 significantly increased the burrowing and reburrowing times of Littleneck marine clams (Protothaca staminea). Abnormal burrowing behaviour was observed with time-lapse video. Aged (1 day) copper-enriched sediment did not affect clam burrowing time. Copper in sediment porewater declined three days after sediment enrichment to background levels without change in total sediment copper. In a long-term experiment, clams with increased burrowing time into copper-enriched sediment had up to 25% mortality after 12–29 days burial in the sediment. The majority of clam mortality was found in clams burrowing within the first 48 h. Over 7 weeks there was blackening of sediment and clam shells proportional to sediment copper enrichment.

Marine sediment and interstitial water: Effects on bioavailability of cadmium to gills of the clam Protothaca staminea

A study was made to determine first, the kinetics of cadmium sorption on a natural marine sediment and second, the degree to which this sorption as well as interstitial water might effect bioavailability of cadmium to gills of the clam Protothaca staminea. Surface sediment from Sequim Bay, Washington was labelled with Cd 109 and total cadmium concentration determined by radioassay. Gills were added to three types of exposures: 1) control (0.45 um filtered seawater, 2) sediment interstitial water and 3) washed sediment. Prepared samples of gills were counted in a liquid scintillation counter. Results show that addition of a small quantity of washed sediment to the exposure system reduced cadmium accumulation by gills to only 17% of the control. Interstitial water had no significant effect. 1 table, 3 figures (JMT)